A Backward-Compatible Multichannel Audio Codec

Abstract

Abstract-We propose in this paper a backward-compatible multichannel audio codec. This codec represents a multichannel audio input signal by a down mix and parametric data. In order to enable backward compatibility, it is necessary to have the possibility of exerting control over the down-mixing procedure. At the same time, in order to achieve a high coding efficiency, both signal and perceptual redundancies should be exploited. In this paper, we describe a codec that unifies the above-mentioned conditions: backward compatibility and exploitation of both signal and perceptual redundancies. The codec combines a high audio quality and a low parameter bit rate. Moreover, its design is flexible, examples of which are the scalability of the audio quality to (in principle) transparency and the possibility to preserve the correlation structure of the original input signals by using synthetic signals. A stereo backward compatible version of the proposed codec is used as a component of the recently standardized MPEG Surround multichannel audio codec.

Binaural Rendering in MPEG Surround

“…The second type (TTT block) represents three input signals (typically, a left, right and center signal) as a stereo downmix accompanied by two channel prediction coefficients (CPCs) that enable decoder-side prediction of a third signal from the two downmix channels. A possible prediction loss may be compensated for by transmission of an additional ICC parameter (see [14,16,17,25] for more details).…”

Compensation of unmasking noise for scalable transmission of three-dimensional multichannel sound

“…Since it was designed for low-bitrate coding, the basic MPEG surround is not suitable for high-quality coding. Although MPEG surround is also applicable to high-quality coding by transmitting the predictive residual signal with the downmixed signal [9], it does not tolerate the desirable downmix for the home reproduction of 3D sound because it requires a specific downmix matrix.…”

Coding and transmission of three-dimensional sound using its spatial features

“…It usually transmits a twochannel down-mixed signal with the spatial parameters of the sound in low-bit-rate coding. Although it is also possible to transmit the predictive residual signal with the down-mixed signal for high-quality coding [2], it does not tolerate the desirable down-mix for the home reproduction of 3D sound because it requires a specific down-mix matrix.…”